Process for converting monoalkyl-substituted monocyclic naphthenes



United States Patent iliobcrt Z. White, San Francisco, Catli assignor to (Sali fornia Research (Corporation, ar: Francisco, @alifl, a corporation of Delaware No Drawing. Filed dune 23, Moll, her. No, 39,213

Claims. Cl. ase se This invention relates to the conversion of naphthenic hydrocarbons and, more particularly, to the conversion of monoalkyl-substituted monocyclic naphthenes to produce lower molecular weight naphthenes and isoparamns.

The present invention is directed to a process for selectively converting, in high yields, a hydrocarbon feed consisting predominantly of monoalkyl-substituted monocyclic naphthenes containing at least 5 alkyl carbon atoms disposed in an alkyl group to a hydrocarbon reaction product composed of parafiinic hydrocarbons and naphthenic hydrocarbons. The paraifinic portion of the product consists predominantly of isoparalhns containing at least 4 carbon atoms per molecule and further, contains only a minor proportion of parafiins containing less than 4 carbon atoms per molecule. The naphthenic portion of the reaction product contains at least 60 mol percent of lower molecular weight naphthenes per mol of feed naphthenes converted to lower molecular Weight products. The process comprises contacting the feed, preferably in the presence of added hydrogen, with a cracking catalyst at supcratmosphcric pressures and at elevated temperatures below about 700 F.

It has now been found that if the hereinafter-described reaction conditions and catalysts are employed in the subject process, the specified monoalkyl-substituted monocyclic naphthenes are selectively converted to a product consisting essentially of isoparafiins and lower molecular weight naphthenes. Surprisingly, it has been found that the reaction produces almost negligible amounts of propane, ethane or methane. Thus, the process is not one of simple dealkylation and this is emphatically shown by the conversion of a feed stock that would lead one skilled in the art to believe that only simple dealkylation would occur upon cracking. Thus, normal decyl cyclohexane, when converted according to the process of the present invention, produces large amounts of lower molecular weight monocyclic naphthenes and isobutane with virtually no nonane or decane appearing in the product.

Even more striking, it has been found that if the feed stock is predominantly composed of monoalkyl-substituted monocyolic naphthenes containing n carbon atoms per molecule, wherein n is a number from 11 to 12, such a feed will be selectively converted to produce a synthetic hydrocarbon product boiling below 100 F., that is predominantly isobutane, and a synthetic portion boiling from 100 F. to just below the initial boiling point of the naphthenes in the feed stock that is predomiantly monocyclic-naphthenes containing 12-4 carbon atoms per molecule.

As previously defined, the feed stock employed in the pro ess is one that is predominantly composed of monoalkyd-substituted monocyclic naphthenes containing at least 5 alkyl carbon atoms disposed in an alkyl group. lit is preferred that the feed stock contain at least 75 mol percent of such naphthenes and, even more preferably, in excess of 99 mol percent. Additionally, it is preferred that tne feed stock be essentially free of such known catalyst poisons as water, oxygen, nitrogen, and the like.

Representative compounds that may be employed in the feed stock of the present invention, either alone or in mixture, are substituted cyclopentanes and cyclohexice anes, such as amyl, hexyl, octyl, decyl, and others that obviously fall within the defined class of naphthenic feeds.

The catalyst employed in the conversion process of the present invention is one which is generically referred to as a cracking catalyst. As used herein, the term,cracking catalyst refers to catalysts that, catalyticaily crack, or reduce in molecular weight, hydrocarbon feed fractions. The term includes both petroleum cracking catalysts and petroleum hydrocracking catalysts, the latter being catalysts that promote cracking in the presence of added hydrogen.

Suitable cracking catalysts for the process of the present invention are petroleum cracking catalysts which may be selected from a variety of solid materials of the type having high cracking activity. Among solid compositions which can be used are the various siliceous cracking catalysts, acid-activated aluminas, those wherein alumina is chemically bonded to aluminum chloride, fiuorided magnesium oxide, and aluminum chloride, particularly when contained within the pores of a support, such as charcoal, so as to reduce vaporization of the aluminum chloride.

in general, it is preferred to employ a solid siliceous material as the petroleum cracking catalyst. For example, there may be used composites of silica-alumina, silicamagnesia, silica-a1umina-zirconia, acid-treated clays, and the like, as well as synthetic metal aluminum silicates (including synthetic chabazites normally referred to as molecular sieves) which have been found to impart the necessary degree of cracking activity. Particularly preferred siliceous cracking catalysts are synthetically-prepared silica-alumina compositions having a silica content in the range of from about 40 to by weight.

In addition to the petroleum cracking catalysts, it has been found that petroleum hydrocracking catalysts are suitable, and normally preferred, for use in the present process. Basically, these catalysts are composed of an acid material having hydrogenating characteristics and hi h cracking activity. These hydrocracking catalysts are generally made up of petroleum cracking catalysts as supports upon which hydrogenating components have been disposed. Accordingly, the solid petroleum cracking catalysts described hereinbefore are suitable for use as the support for the petroleum hydrocracking catalysts of the present invention. The preferred cracking catalysts hereinbefore described are also preferred for use as the petroleum hydrocracking catalyst support.

Broadly speaking, the hydrogenating component of the petroleum hydrocracking catalysts may comprise one or more of the metals, and compounds of such metals, in groups Hi3), 11(8), V, VI, VII, VIII of the Periodic Table. Further, it is preferred that the hydrogenating component of the catalyst be selected from one or more of the various compounds of metals falling within the aforesaid groups which are not readily reduced to the corresponding metal form under the preferred reducing conditions prevailing in the conversion zone. Thus, while the invention is operable with catalysts such as those having nickel oxide or cobalt oxide which are readily reduced in the presence of hydrogen to the corresponding metal form in the conversion zone, it is preferred to use compounds not readily reduced, such as an oxide or sulfide of molybdenum, tungsten, chromium, rhenium or zinc, or a sulfide of cobalt, nickel, copper, or cadmium: other hydrogenating materials falling within this preferred category are complexes of the various metals of the defined groups, such, for example, as cobalt-chromium, and nickel-chromium. An exception to the general preference for hydrogenating components that are not reduced to the metal form in the conversion zone is the use of a platinum hydrogenating component disposed upon an alumina support upon which is sublimed aluminum chloride. This later catalyst is particularly preferred for use in the subject process. Also, especially preferred catalysts are those in which nickel sulfide and/ or cobalt sulfide is disposed upon a synthetic silica-alumina cracking catalyst. The amount of the hydrogenating component may be varied within relatively wide limits of from about 0.1 to 35% or more, based on the weight of the entire catalyst composition.

In the operation of the subject process, the feed stock can be introduced to the reaction zone as either a liquid, vapor, or mixed liquid-vapor phase, depending on the temperature, pressure, proportions of hydrogen, and boiling range of the feed stocks. Although the presence of added hydrogen is not necessary, it is preferred that the feed be introduced in an admixture with at least 750 s.c.:[. of hydrogen per barrel of total feed, and even more preferably, with from 1000 to 2000 s.c.f. per barrel of feed. When employed, the hydrogen stream admixed with the incoming feed is conventionally made up of recycled gas recovered from the effluent of the reaction zone, together with fresh make-up hydrogen. The hydrogen content of the recycle gas stream, in practice, generally ranges upwardly of 7 volume percent.

Pressures employed in the conversion zone are at least 175 p.s.i.g., and may range upwardly to as high as 2500 p.s.i.g., or higher, with a preferred range being a total pressure of from about 500 to 1800 p.s.i.g.

Generally, the conversion zone feed stock may be introduced into the reaction zone at an LHSV of from about 0.1 to v./ v./ hr. (volumes of hydrocarbon calculated as liquid per superficial volume of catalyst) with a preferred rate being from about 0.5 to 8 v./v./hr.

One of the most important aspects of the present process is that the reaction is conducted at considerably lower temperatures than is generally associated with cracking reactions. Thus, it has been found that the conversion zone should be maintained at elevated temperatures below about 700 F., and preferably below 600 F. It has been found that at temperatures above about 650 F., converting the feed stocks by the subject process leads to increased ring rupture, thereby reducing the total number of ring structures in the product and increasing the production of relatively low boiling isoparaffins. Although the latter are predominantly isobutanes, the production of lower boiling naphthenic compounds is reduced.

EXPERIMENTAL A number of experimental runs were made on the conversion of pure, monoalkyl-substituted monocyclic naphthenes. These feeds were selected since they more emphatically showed the surprising aspects of the present invention. The runs were made in a continuous flow, fixed bed, high pressure, microcatalytic unit. The 6 ml. of catalyst was supported inside of 0.79 cm. I.D. stainless steel tube which was surrounded by a heavy-walled steel block inside an electrically heated oven. Catalyst temperatures were measured by a chromel-alumel thermocouple located on the reactor wall at the central portion of the catalyst bed. Hydrocarbon feed rates were measured by a microfeeder pump and the hydrogen rate was measured by oil displacement in a reservoir.

Liquid products were analyzed by gas chromatography and the accuracy of the method confirmed by analysis of known mixtures of similar hydrocarbons. The gaseous portion of the product was analyzed by mass spectrometry.

Of the following six separate catalysts, only Catalyst A was employed in the run set forth in the examples. However, all of the other catalysts can be employed to attain the desired results.

Catalyst A.'Phis hydrocracking catalyst, preferred for use in the subject process, was prepared by impregnating 126 cubic centimeters of silica-alumina (about 90 percent silica and 10 percent alumina) cracking catalyst fines with a solution of nickel nitrate to dispose 6 weight percent nickel on the catalyst support. The catalyst was dried in a kiln to 600 F. and then heated (thermactivated) by contact for 2.2 nouns with hot air (15 s.c.f./min.) at an average temperature of 1427 F. The nickel oxide was then reduced by contacting the catalyst with once-through hydrogen (1.6 cubic feet/hour) at atmospheric pressure while heating from to 570 F. at 100 F. per hour, and thereafter contacting the catalyst with hydrogen (1.6 sci/hr.) at 1500 p.s.i.g. and 570 F. for one hour. Sulfiding of the nickel component was performed by contacting the catalyst with a solution (66 cc./hr.) of 2.6 theories of 10 weight percent isopropyl mereaptan in hexane for 3.5 hours at 1500 p.s.i.g. and 570 F. Hydrogen (2.22 sci/hr.) was sirrrultaneousiy passed over the catalyst at a rate so as to give 2 percent H S in the gas.

Catalyst B.-This catalyst was prepared in the identical manner as Catalyst A except that, following reduction of the nickel oxide to nickel metal, no sulfiding was done. Thus, Catalyst B was composed of 6 weight percent metallic nickel disposed on the cracking support.

Catalyst C.This hydrocracking catalyst was prepared by impregnating 120 cc. of synthetic silica-alumina (about percent silica and 10 percent alumina) 8-14 mesh cracking catalyst tempered for 24 hours at 1400 F. (in dry air) with a solution of nickel nitrate. The nickel on the catalyst amounted to 5.3 Weight percent of its total weight. The catalyst was then dried for 10 hours at 250 F. and 10 more hours at 1000 F. The nickel oxide was then reduced by (1) contacting the catalyst for /2 hour at 500 F. and atmospheric pressure with 6 cubic feet per hour of hydrogen, and (2) contacting the catalyst for one hour at 580 F. and 1200 p.s.i.g. with about 0.ll cubic feet per hour of hydrogen. The nickel was then substantially sulfided by contacting the catalyst for 3 hours at 580 F. and 1200 p.s.i.g. with 0.33 s.c.f./hour of 2 percent H S in hydrogen.

Cazalyst D.-This hydrocracking catalyst was prepared by impregnating A -inch alumina extrudate with a nickel nitrate solution. The nickel on the catalyst amounted to 6.66 weight percent of the entire weight of the catalyst. The latter was dried for 20 hours at 400 F. at atmospheric pressure and then calcined by heating for 4 hours at 900 F. at atmospheric pressure. The nickel oxide was then reduced by contacting the catalyst with about 0.1 s.c.f./hour of hydrogen at 900 F. and about 1100 p.s.i.g. The catalyst was then sulfided in situ (in the reactor) by passing feed and dimethyl disulfide in the reaction zone. After 4 hours, the disulfide was cut off an ER and feed, at a ratio of 1:10, was fed with hydrogen to the reaction zone at a rate of 6 mL/hour at a pressure of 1185 p.s.i.g. (B1 partial pressure 12 p.s.i.g.). Thus, the catalyst was a BP -activated alumina support having a nickel sulfide hydrogenating component disposed thereon.

Catalyst E.-This petroleum cracking catalyst was simply a conventional cracking catalyst of 814 mesh synthetic silica (about 90% )-alurnina (about 10%) that was employed in the hydrocracking-type Catalysts A, B, and C as the catalyst support.

Catalyst F.This preferred catalyst is prepared, for example, by the method described in Union of South Africa iatent No. 834 which comprises subliming aluminum chloride onto a preformed composite of platinum and fiuorided alumina, and heating the treated composite at a temperature of from about 750 to 1100 F. for a time (generally in excess of one hour) until substantially all of the unreacted aluminum chloride has been removed. The catalyst contains about weight percent alumina, about 036 Weight percent platinum, about 4.4 weight percent chloride and about 0.32 weight percent fluoride (all weight percents are based on the weight of the entire catalyst).

Example 1 Essentially pure normal decyl cyclohexane was contacted (in the above-described apparatus), along with 12.4

mols of hydrogen per mol of feed at a hydrogen rate of 6403 s.c.f./barrel of feed, with Catalyst A at a tem perature of 450 F., a pressure of 1185 p.s.i.g., and an LHSV of 8.0 v./v./hr. (Run 736). One hundred percent of the feed was converted to lower molecular weigh products. The analysis of the entire hydrocarbon reaction product is given in Table l below.

Example 2 Essentially pure normal decyl cyclopentane was contacted with the same catalyst and under identical reaction conditions (except that the feed was contacted along wtih 10.8 mols of hydrogen per mol of feed at a hydrogen rate of 6660 s.c.f. per barrel of feed) as in Example 1. In this run (737), 100 percent of the feed was converted to lower molecular Weight products. The analysis of the entire hydrocarbon reaction product is shown in Table 1.

Product, Mole/100 Mols Feed Run N0. Run N o.

Methane r r-u- H M O r pss s pppepe-i s s From the data disclosed in Table I, the selective nature of the subject process is shown by the various rnol percent calculations set forth in Table ll.

TABLE 11 Run 737 Run 7136 Mol percent C -paraifms in paraifinic portion of product 3 4 M01 percent (Jrparalllns in hydrocarbon product boiling below 100 F 6 7 M01 percent 0 isoparal-Iins in parallnic portion of product 94 93 M01 percent C -lnormal parallins in parailinic portion of product. 3 3 Mol percent lower molecular Weight naphthenos in product boiling from 100 F. to below initial boiling point of naplithenos in feed 70 70 M01 percent lower molecular weight naphthenes per mol of feed naphthenes converted 125 110 As can be seen from the calculations of Table II, the recess of the present invention produces extremely small quantities of C and lighter hydrocarbon gases, and that the paraliinic portion of the reaction product containing 4 and more carbon atoms varies from 93 to 94 mol percent isoparafilns whereas the normal paraffins only amount to 3 or 4 percent. Further, it is apparent that the naphtllenic portion of the product contains considerably in excess of 60 R101 percent lower molecular weight naphthenes per mol or feed naphthenes converted.

Example 3 Essentially pure tertiary amyl cyclohexane was contacted, along with 9.5 mols of hydrogen per mol of feed at a rate of 6745 s.c.f. per barrel of feed, with Catalyst A at a temperature of 453 F, a pressure of 1185 p.s.i.g. and an LHSV of 8.0 v./v./hr. (Run 603). A conversion d of 31.2 percent to lower molecular weight products was obtained. The analysis of the entire hydrocarbon reaction product is given in Table III.

TABLE III Product, mols/ 100 mols of feed: Run 603 Methane 0 Ethane 0.02

Propane 0.4 lso-butane 12.0

n-Butane 1.5 Iso-pentane 5.8 n-Pentane 0.2

Iso-hexane 0.7

n-Hexane 0 lso-heptane 0.2 (3 pararlins 0 Cyclopentane 0 Methyl cyclopentane 5.4 Cyclohexane 1.6 Methyl cyclohexane 16.7 Ethyl cyclopentane 1.2 Di'nethyl cyclopentane 7.8

Total C naphthenes 68:8

From the data set forth in Table Ill, the various results shown in Table lV can be calculated.

TABLE IV Moi percent C paratfins in parai'linic portion of product 2 M01 percent C paramns in hydrocarbon product boiling below 100 F. 2

Mol percent (3 isoparafiins in paraffinic portion of product Mol percent C lnormal paraffins in parallinic portion of product 5 M01 percent lower molecular weight naphthenes in product boiling from 100 F. to below initial boiling point of naphthenes in feed M01 percent lower molecular weight naphthenes per mol of feed naphthenes converted M01 percent n-4 naphthenes in product boiling from 100 F. to just below initial boiling point of naphthenes in feed Mols n-4 naphthenes per mol of feed naphthenes converted 0.83

As in the previous runs, the data clearly show the low C paraffin production and the very high proportion of C plus isoparaifins in the paramnic portion of the reaction product. Also, the naphthenic portion of the reaction product contains considerably above 60 inol percent lower molecular weight naphthenes per mol of feed naphthenes converted.

The data presented in Tables ill and IV also show that when the feed is a rnonoallcyl-substituted monocyclic naphthene containing n carbon atoms per molecule, wherein n is a number from 11 to 12, in this case n is equal to 11, that the synthetic portion of the product boiling from 100 F. to just below the initial boiling point of the feed is predominantly composed of monocyclic naphthenes containing 21-4 (7) carbon atoms per molecule. Thus, it can be seen from Example 3, that tertiary arnyl cyclohexane cracks to produce such a product that contains 61 rnol percent of C naphthenes. Further, for every mol of feed converted, 0.83 mols oi n4- (C naphthenes are produced. it will also be noted that the mol ratio of methyl cyclohexane to methylcyclopentane is well over unity, namely, about 3.

1 claim:

1. A process for converting a hydrocarbon feed cornprising over 50 percent of monoalkyl monocyclic naphthenes containing at least alkyl carbon atoms disposed in an alkyl group to a hydrocarbon reaction product composed of paraflinic hydrocarbons and naphthenic hydrocarbons, the parafiinic portion of said product consisting predominantly of isopa-raffins containing at least 4 carbon atoms per molecule and containing only a minor proportion of paraflins containing less than 4 carbon atoms per molecule, and the naphthenic portion of said product containing at least 60 mol percent of lower molecular weight products, which comprises contacting the feed With a solid cracking catalyst at superatmospheric pressure and at elevated temperatures of from 360 to about 700 F.

2. The process of claim 1, wherein the naphthene portion of the product contains a mol ratio of methylcyclohexane to methylcyclopentane greater than 1.0.

3. A process for converting a hydrocarbon feed comprising over 50 percent of monoalkyl monocyclic naphthenes containing at least 5 alkyl carbon atoms disposed in an alkyl group, which comprises contacting said feed in a reaction zone with a solid cracking catalyst at a temperature of from about 360 to about 700 F., a pressure of at least 175 p.s.i.g., and at a liquid hourly space velocity above 0.1 v./v./hr., recovering the effluent from said zone wherein the hydrocarbon portion boiling below 100 F. is predominantly isobutane and the synthetic portion of said effluent boiling from 100 F. to just below the initial boiling point of the naphthenes in said feed is predominantly naphthenic hydrocarbons having a molecular Weight less than the naphthenic hydrocarbon in the initial feed.

4. The process of claim 3, wherein the hydrocarbon portion of the eflluent boiling below 100 F. contains less than mol percent of C through C paraflins.

5. The process of claim 3, wherein the portion of the effluent boiling from 100 F. to just below the initial boiling point of the naphthenes in the feed contains a mol ratio of methylcyclohexane to methylcyclopentane gerater than 1.0.

6. The process of claim 3, wherein said feed is contacted in said reaction zone along with at least 750 s.c.f. of hydrogen per barrel of feed.

7. A process for converting a feed strock comprising at least 75 mol percent of monoalkyl-substituted monocyclic naphthenes containing 11 carbon atoms per molecule, wherein n is a number from 11 to 12, which com prises contacting said feed stock, along with at least 750 s.c.f. of hydrogen per barrel of said feed stock, in a conversion zone with a solid cracking catalyst at a temperature of from about 360 F. to about 650 F., a pressure of at least 175 p.s.i.g., and at a li'quid hourly space velocity above 0.1 v./v./hr., recovering the effiuent from said zone wherein the hydrocarbon portion boiling below F. is predominantly isobutane and the synthetic portion boiling from 100 F. to just below the initial boiling point of the naphthenes in said feed stock is predominantly monocyclic naphthenes containing n-4 carbon atoms per molecule.

8. A process for converting a feed stock comprising at least 75 mol percent of monoalkyl-substituted monocyclic naphthenes containing 12 carbon atoms per moleeule, wherein n is a number from 11 to 12, which comprises contacting said feed stock, along with at least 750 s.c.f of hydrogen per barrel of said feed stock, in a conversion zone with a catalyst comprising a hydrogenating component selected from the group consisting of nickel sulfide and cobalt sulfide disposed on a solid, active, acid support at a temperature of from about 360 to about 650 F., a pressure of at least 175 p.s.i.g., and at a liquid hourly space velocity above 0.1 v./v./hr., the efiluent from said zone boiling below the initial boiling point of said feed stock containing at least 0.5 mol of monocyclic naphthenes containing n-4 carbon atoms per molecule for every mol of feed stock naphthenes containing n carbon atoms per molecule cracked to lower molecular weight products.

References Cited by the Examiner UNITED STATES PATENTS 2,422,674 6/47 Haensel et al. 260-666 2,428,692 10/47 Voorhies 208-112 2,849,504 8/58 Kang et al. 260666 2,987,466 6/61 Senger et al. 208

OTHER REFERENCES Egloff: The Reaction of Pure Hydrocarbons, pp. 720'- 721 relied on, Reinhold Publishing Corporation, New York, 1937.

ALPHONSO D. SULLIVAN, Primary Examiner.

DANIEL E. WYMAN, MILTQN STERMAN,

Examiners. 

1. A PROCESS FOR CONVERING A HYDROCARBON FEED COMPRISING OVER 50 PERCENT OF MONOALKYL MONOCYCLIC NAPHTHENES CONTAINING AT LEAST 5 ALKYL CARBON ATOMS DISPOSED IN AN ALKYL GROUP TO A HYDROCARBON REACTION PRODUCT CONPOSED OF PARAFFINIC HYDROCARBONS AND NAPHTHENIC HYDROCARBONS, THE PARAFFINIC PORTION OF SAID PRODUCT CONSISTING PREDOMINANTLY OF ISOPARAFFINS CONTAINING AT LEAST 4 CARBON ATOMS PER MOLECULE AND CONTAINING ONLY A MINOR PORPORTION OF PARAFFINS CONTAINING LESS THAN 4 CARBON ATOMS PER MOLECULE, AND THE NAPHTHENIC PORTION OF SAID PRODUCT CONTAINING AT LEAST 60 MOL PERCENT OF LOWER MOLECULAR WEIGHT PRODUCTS, WHICH COMRPISES CONTACTING THE FEED WITH A SOLID CRACKING CATALYST AT SUPERATMOSPHERIC PRESSURE AND AT ELEVATED TEMPERATURES OF FROM 360* TO ABOUT 700*C. 